Device for the automatic adjustment of the tensions of films



Dec. 30, 1930. E. OEHMICHEN 1,736,917

DEVICE FOR THE AUTOMATIC ADJUSTMENT OF THE TENSIQNS OF FILMS Filed Aug. 9, 1927 2 Sheets-Sheet l Dec. 30, 1930. E, OEHMICHEN 1,786,917

DEVICE FOR THE AUTOMATIC ADJUSTMENT OF THE TENSIONS OF FILMS Filed Aug. 9, 1927 2 Sheets-Sheet 2 Fig. 2.

1 v veA/TaR Patented 30, 1930 UNITED STATES PATENT OFFICE ETIENNE OEHMICHEN, OI V ALENTIGNEY, FRANCE manor: iron. 'rn'n auroua'rrc Amosrumwr or ran TENSIONB or runs Application filed August 9, 1927, Serial No. 211,803, and in France August 17, 1926.

The present invention has for its object a device for winding or unwinding any kind of soft strip and particularly a cinematographic film, the arrangement of this device v being such that the tension of the film will be automatically adjusted.

According to this invention, this adjustment is obtained in causing alternately the braking or the setting in motion, by means of-an independent motive power, of the film carrying spool, through the action of the displacements of a regulating member, on both sides of its position of balance and which is acted upon by the film or strip through the medium of a change of direction efi'ected upon the said regulating member.

The same principle can be applied in various manners without departing from the invention and the appended drawing shows, by way of example, several embodiments which appear as being different although they are based in a direct manner upon the same principle.

Fig. 1 is a perspective view of a first embodiment.

Figs. 2 to 7 refer to modified forms.

From the free portion of the strip which is to be wound or unwound (Fig. 1) is derived a loop 1 included between two stationary rollers 2 and within which is disposed a movable roller 3 under the elastic control of any means (spring, counterweight, or the like) so as to keep the loop in a stretched state; the movements of this stretching roller control a device capable of determining or of stopping the movements of the spool containing the film to be wound or'unwound. I In the unwinding operation, the whole is combined in such manner that the setting in motion of the spool 4 takes place when the loop 1 tends to diminish in length and stops when on the contrary the latter tends to extend. I

1 In the winding operations, the drives are reversed, the result remaining the same.

By wayof example, the case of winding can be taken into consideration: the movements of the roller forming the loop determine the braking of the planetary pinion carryin drum 5 of a differential gear, whereo the lateral rings are the one 6 securedto the spool, and the other 7, to an independently driven shaft.

When the loop tends to be reduced in length, in virtue of too great a return of the strip, the roller, through any suitable trans mission of motion, loosens the brake 8 acting upon the drum carrying the planetary pinions, at same time this roller acts upon a second brake 9 slowing down the movement of the winding spool. The drum carrying the planetary pinlons, when made loose, can no longer transmit its rotary motion to the spool which is on the other hand braked; the said spool then slows down thereby allowing the loop to reassume its normal length.

On the contrary, if the spool does not Wind a suflicient quantity of strip, the loop extends, this having for effect to apply the brake of the planetary pinion carrying drum and to immobilize the same gradually, the brake 9 of the spool being at the same time loosened.

If in consequence of the lengthening of the loop 1 the brake 8 is applied, the planetary drum is progressively stopped; the'move ment which is produced by the independent source is therefore progressively imparted to the winding spool so much completely the more the brakeband is applied upon the planetary-drum. When the latter is stopped the speed of the spool is at its maximum. The tendency of the spool to keep this maximum speed continues as long as the braking effect is exerted upon the planetary drum, that is to say that the loop has not got itsnormal length which corresponds to the normal stress of the film.

If the apparatus is conveniently regulated, 99 very small elongating and shortening movements of the loop will be sufficient to deter mine the feeding or stopping operation of the spool and it will be possible to obtain a practically constant tension whereof the value can be extremely reduced, the roller exerting its stresses only for operating'two brakes which allow powerful effects to be obtained, while requiring but a very small op erating stress.

The same mechanism can be used for unwinding purposes in reversin the drives, that is to ea 11'! causing the bra e to act upon the ring of tire differential gear when the loop tends to extend and in loosening the sai brake when the said loop tends to become shorter.

A modified form of the device, is indicated in Figure 2 in which the planetary pinion carrying drum 5a receives the motion tobe transmitted throughapulley a, a toothed wheel or any other means, and in which the brake drums 11 and 12 are secured to the shafts carrying the rings of the differential gear. The motion or the stopping of the spool 4 can be obtained in alternatively actin upon the brakes 13 or 14, by means of the roller device 3 (Fig. 1)

Finally, the differential gear can be replaced by a simple friction clutch combined with a brake. F1 ure 3 shows an example of this arrangement in which a friction plate 15 operated by a fork 16 and slipping upon the shaft 17 driving the pulley 4e and connected with this shaft throu h the medium of a long key or of a cone, can engaged with a drum or a plate 18 which is independently operated or can be braked, in 19, the movements of the fork 15 being in relation with those of the roller 3 (Fig. 1). a

In the case of differential gears 5", 6, 7", (Fig. 4) for example, the principle of the invention can be carried out in usin two electro-ma ets 28*, 29" connected wit any supply of electric current and controlling each the brake bands 8 9 acting upon the ring carrying the planetary pinions 5" or upon the shaft carrying the spool 4". These two electro-magnets are put in circuit so as to correspond to ositions as close together as can be desired of the regulating roller 3" and thereby allowin an adjustment which is as perfect as possi 1e.

Alterations can be made in the same way in the mechanical driving systems. Thus the device with differential gfar can be made of spur wheels in the well nown manner; the planetary pinions are then to be pairs between the wheels 6 and cated in Figure 5.

Fig. 6 shows also an embodimentof the invention with a differential gear which is more flat than the previous one. The same comprises a planetary train with epicycloidal gears. As in the case of the differential gear,

grouped in as indithe system can transmit power or not, accord ing as the planetary pinion carrier 5 is immobilized or released. Such a'device can furthermore be acted upon otherwise, without departing from the principle. For example, the drive can be effected by the external ring, the planetary pinion carrier being released or made idle, or by the planetary pinion carrier itself in releasing or renthe whole of this would be imparted to the dering idle either the external ring or the external pinion, and so on.

In this case as in the case ofthe difierential gear, the mechanism comprises a train of gear wheels with planetary motion or not, composed at least of three parts, the first one of which is constituted by the drivingshaft and its pinion 7 the second one by the shaft of the spool and the corresponding gear 6, and the third one by a part 5 carrying pinions which mesh with the two first ones and is capable of being immobilized or made idle by the play'of the brakes operated by the regplating roller.

inally, in order to simplify the device and to avoid the drives requiring alinements, let us suppose as being collected upon forked member 38, a drivin roller 39 operated by a flexible shaft 40 and actin u n a plate 41 connected to the spool 4 an a aking member 42 (Fig. 7). t is only necessary to cause device to swing about an axis 43 to cause the bearing of the roller against the plate to impart motion while the bearing 0 the brake stops the same. The alternative movement of oscillation and of translation of the art carrying the driving roller 3' and the rake 42 is controlled by the regulating roller 3'.

Of course, all these devices are but modified foFms of the main device and have been indicated but for thesake of clearness. In fact they are all based upon the principle of the braking of the spool or of the setting in motion of the latter under the influence of the displacements of the regulating rolleron both sides of its position of balance.

In all cases, the setting in motion. or the stopping must take place within a very .short period of time and with-ve small displacements of the-roller. The atter must only require, in order to determine the startin or stopping of the s 001, but very smal stresses, otherwise etrimental tensions, which it is precisely the purpose to .avoid,

strip.

Therefore, it is necessary for theroller to have only to drive parts answering at once with the maximum of action and the minimum of displacement. 4 The control of a brake band the windin of which can reach and even exceed a circumference and which can consequent] stop a powerful motion witha very small pu of the free run, the closing of an electric contact, the operation of a valve or of atap, and the like, are precisely fulfilling the required conditions.

The driving power derived from an external supply can thus be wholl transmitted to the spool or suppressed wit very small values of the stroke and of the st of the regulating roller.

It is obvious that the devices as described can all be gathered upon a same member its - differential gear comprisin three memberslike, the combinationof a that is to say two central w eels and a planetary pinion carrier-the one of these members being coupled with the said film spool, driving-mean for rotating a second of-the said means controlled b the variations of tension of the film, said riving means comprising clutching means and said means controlled by the variations of tension of the film being adapted to operate both the said clutching means and the said brake so as to unclutch the driving means at the same time the spool is braked and to clutch the driving means at the same time the brake is released.

In testimony whereof I have hereunto affixed my signature.

ETIENNE OEHMICHEN.

members a brake cooperating with the member coup ed with the spool, a second brake coo crating with the third member of the sai difierential gear and means controlled by the variations of tension of the film and adapted to control both the two said brakes so .as to apply the one while the other is released.

2. In acinematographic a paratus or the like, the combination of a m spool, a'differential gear comprising a toothed wheel coupled with this spool, a second toothed wheel and a planetary pinion carrier, means for rotat ng this said second toothed wheel, a brake. ada ted to brake the system of the spool and o the wheel coupled therewith, a second brake adapted to brake the planetary pinion carrier, and means controlled by the variations of tension of the film and adapted tosimultaneously control'the two brakes so as to apply the one and release the other.

3. In a cinematographic apparatus orthe lm spool, an e icycloidal diflerential' gear comprisin tree members-that is to say two. centra wheels and a planetary'pinion carrier- -the one of these members being coupled with the Y said film spool, driving means for rotating a second of the said members, a'brake oooperating with the member cou s ool, a second brake cooperatm with the t ird member of the said epicy oidal gearand means controlled .by the variations of tension of the film and adapted to control both the two said brakes so as to apply-the one while the other is released. v

j 4. In a cinematographic apparatus or the like, the combination of a film spool, driving means for rotating this spool, braking means for braking the said spool, and means controlled by the variations of tension of the film and adapted to control both the said drivpled with the ing. means and braking means, so asto apply 7 the one while thelother is released.

I like, the combinationo hie apparatus or the "a filmspool', driving means-fer rotating this spool, a brake for braking the rotation of the said spool, and

5. In a. cinematograp 

